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Message Posted: Thu, 22 May 2003 @ 18:37:29 GMT


     
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Subj:   Re: Time Stamp in Teradata
 
From:   Dieter Nöth

Geoffrey Rommel wrote:

  So if you select without ORDER BY you'll always end up with an unordered result set. This is different to most other RDBMSes.  


  I hesitate to disagree with Dieter, but this is not quite correct.  



You're welcome, don't hesitate ;-)


  In relational theory, relations are sets, so they are unordered. For instance, the set {integers between 1 and 20} can be enumerated in a conventional order -- 1, 2, 3, etc. -- but there is no order to the set itself; all 20! enumerations specify the same set.  


Yep: "So if you select without ORDER BY you'll always end up with an unordered result set."


  In other RDBMSes, the rows may in fact come out in the same order every time,  


even in Teradata


  but this is merely a by-product of the physical ordering on disk; it does not imply that there is an order to the rows of the table.  


Yep: "This is different to most other RDBMSes."

Teradata is just closer to the relational model than other databases ;-)

So, i really don't see where we disagree.


Dieter



     
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